Method of manufacturing hollow articles from metals



Patented Feb. 13, 1940 UNITED STATES PATENT OFFICE METHOD OFMANUFACTURING HOLLOW ARTICLES FROM METALS Drawing. Application November23, 1937,

Serial No. 178,143. In Germany November 6,

This invention relates to the manufacture of hollow bodies, inparticular cartridge cases, shell cases and the like, from metals,especially nonferrous metals. As is well known, such cases are made fromcircular discs which are shaped in I numerous pressing and drawingstages.

The usual method is tostamp the circular discs from a sheet of metal.The raw material has to pass through many stages before it is convertedinto the form of a sheet. The metal must be melted and cast, the ingotsmust be milled and then hot rolled and pressed and cold rolled. Thediscs are then stamped out and annealed. Only when this has been done,can theactual work of cold shaping be begun. The actual manufacturingcosts of the circular discs are considerably increased owing to theamount of waste produced. The weight of the waste formed during thestamping is at least equal, under ordinary conditions, to the weight ofthe finished discs. In most cases it is greater.

Now, it has previously been proposed to form the discs by sawing rolledor pressed and drawn bars instead of by stamping the discs out of sheetmetal. In this way it is true that the waste produced in stamping thediscs out of the sheet metal is avoided, but this advantage is off-setby the disadvantage that, in pressing these heavy bars, 25 to 40% ofwaste is produced. In the extrusion press alone, a waste of 25 to 35%must be reckoned on, in the case of bars of the large diameter which arehere in question, to which must also be added the dead heads lost incasting, the loss by burning and so forth which may amount to from to%.This method of operation therefore has no advantage, over the method ofmanufacture from rolled sheets, especially when the cases are made ofnon-ferrous metals,

and therefore the method has not come into practical use.

According to the present invention, the circular discs which are used asthe starting material for 1 Claim. (01. 29-13) the like. The shaping ofthe discs as well as the necessary annealing between the shapingstepsensures that the material undergoes recrystallisation in the courseof the process which has been found by experience to be advantageous.

Particularly good results are obtained if a copper-zinc alloy containingabout 72% copper is employed, with which additional substances whichmake the grain finer, such as nickel, iron or lead are alloyed, and ifthe cast bars are cooled down rapidly after casting. I

In order to avoid roughening the surface of the discs having a caststructure when they are being shaped, it is advisable to carry out thefirst shaping or deformation step either at room temperature or at anelevated temperature which is below the usual hot working temperature.It is also desirable to effect very high degrees of deformation followedby recrystallisation annealing at relatively low annealing temperaturesin the various stages in order to obtain a final productof which thequality is equal to that produced from sheet metal.

Usually the cast bars will have the same diameter as the circular discswhich are subjected to the shaping operations are to possess. -Ingeneral it is not necessary to remove the casting skin by turning,because this skin is in any case removed during the ordinary course ofmanufacture of the case. If, however, removal of the skin is required,then the diameter of the cast rod must obviously be correspondinglygreater.

It is possible by means of the new process to manufacture cartridge andlike cases with a considerable saving of metal and work. There is thefurther advantage that the alloys, for example of copper and zinc, maycontain a larger amount of foreign materials than is otherwisepermissible since with the new process no hot deformation, which isimpaired by the presence of foreign substances, is necessary; as, whenthe usual methods are employed, it is practically impossible tomanufacture sheets from east ingots solely by cold deformation.Therefore, the copper-zinc alloys may contain larger amounts of lead andphosphorus than would otherwise be allowable.

The main advantage of the new process is in the entire elimination ofall rolling Work and the costs thereof, as well as the avoidance of thewaste which is occasioned in the manufacture of rolled plates and thestamping of the discs from these plates.

1 claim:

The process of producing cartridge cases w r ni to the form of cartridgecases and zinc-copper alloys comprising casting a bar of 58 withannealing treatments, the temperature of the alloy in the first drawingoperation being below the usual hot-working temperature of the alloy andthe first drawing operation performing a high degree of deformation toavoid roughening 5 the surface of the articles.

KARL STAIGER.

